Character alignment in cathode-ray display tubes

ABSTRACT

In order to achieve alignment of characters displayed on sideby-side electrostatically deflected cathode-ray indicia tubes, a magnetic centering magnet is used to project a field into the electron gun in the region of the electron beam path. To avoid influencing adjacent tubes the magnet is flat and is placed and held adjacent the outside of the tube envelope in a position to standardize the character position by means of a thin strip or web of low permeability magnetic material having an adhesive backing, thereby limiting the projection of the external magnetic field from affecting other closely positioned tubes.

I United States Patent 13590310 72] Inventor Horst H. Blumenberg 3.081.420 3/1963 Marley .7 313/77 X i Owensboro, Ky. 3.421043 1/1969 Macintyre. Jr. et al 315/18 X 5 1969 Pnmar Exammer--T H Tubbesing [2 l y Assistant Examiner-Brian L. Ribando [45] Patented June 1971 A!!0rnevLaurence R Brown [73] Assignee Kentucky Electronics Corporation Owensboro, Ky.

[54] CHARACTER ALIGNMENT IN CATHODE-RAY DISPLAY TUBES ABSTRACT z In order to achieve alignment of characters (115- 4Clnims 3 Drawing 3S played on side-by-side electrostatically deflected cathode-ray mdlcla tubes, a magnetic centering magnet IS used to pro ect a [52] U.S. Cl 315/18, field into the electron gun in the region of the electron beam 313/77 path [51] Int. Cl HOlj 29/82 To avoid influencing adjacent tubes the magnet is flat and is [50] Fleld 0! Search 313/20, 69, placed and held adjacent the Outside f the tube envelope in a 77? 35/18, 1.69; 340/324 A position to standardize the character position by means of a thin strip or web of low permeability magnetic material having [56] Referenm Cited an adhesive backing, thereby limiting the projection of the ex- UNITED STATES PATENTS ternal magnetic field from affecting other closely positioned 2,875,951 3/1959 Schreiner 340/324 A tubes.

DEF LECTIO N CHARACTER GENERATOR AND SELECTION CIRCUITS PATENTED JUNZS r9?! w. p m M S T m ,EC mm m W AN mmm m T C .R m m E. r v m FIG.I

INVENTOR HORST H.BLUMENBERG BY 6K. 5

ATTORNEY CHARACTER ALIGNMENT IN CATllIODE-RAY DISPLAY TUBES This invention relates to the deflection of electron beams in cathode-ray tubes and more particularly it relates to the alignment of character displays in a plurality of side-by-side character display tubes of the cathode-ray tube type having an electrostatically deflected electron beam.

There are many applications in the electronic arts of data processing, control systems and the like where it is desirable to display output information visually in the form of indicia such as alphanumeric characters. Several known approaches to visual displays are noted which permit readout in response to electrical signals. However, a leading deficiency is the limitation imposed in forming characters with many types of devices having fixed or limited numbers of predesigned characters. For example cathode glow-type indicator tubes can only conveniently display a few characters, and even then some are blocked from view by intervening nonselected characters, and custom built expensive devices are generally necessary for unusual characters such as a dollar sign or a foreign alphabet such as Hebrew or Arabic.

Parallax problems exist with many indicator devices that have several character planes, so that the indicia are only visible from a narrow viewing angle directly in front of the display.

Also space limitations, for many devices displaying a single character, are such that individual characters are difficult to array side-by-side in simulation of spacing aspect ratios normally encountered in printed text for example. It is particularly difficult to produce small characters of less thanl inch in width and height side-by-side without distortion or other deficiency.

Further deficiencies ofindicator devices are:

1. low light levels ifthey self-generate their light source,

2. ability to reflect and operate in the dark if they do not self-generate a source of visible light on or from the character indicia, and

3 rapidity of selection or change from one character to the next in response to electronic signals.

The latter aspect may also include the 'difficulty to synchronize generation ofa desired character or to start at any point in time with the generation ofa selected character.

The cost of producing a satisfactory device solving the foregoing deficiencies in the prior art is a significant factor in the acceptance of any particular approach. For example if an indicating device must be custom made, it becomes expensive, and if it has critical tolerances or assembly problems, quality control may be a serious problem. Also a long life for the indicator is desirable.

It is therefore an object of the invention to produce a flexible character generator improving the state of the prior art and eliminating the foregoing problems and deficiencies.

It is more specific object of the invention to provide a versatile but low cost bright display device that eliminates parallax.

An important objective of the invention is to produce a device which produces a multiplicity of side-by-side characters of predetermined shapes which are closely aligned.

Therefore, in accordance with this invention, there is provided a character display system of side-by-side cathode-ray tubes each displaying separate characters. Each tube has a cylindrical envelope with a high light output phosphorescent coating with a long persistence to produce a single viewing plane in which characters of any shape may be generated at electronic speeds by means of electrostatic beam deflection potentials in response to electrical signals arriving at any predetermined time.

Such tubes may be inexpensively made and universally used, provided they have accurately aligned beams that produce characters in the side-by-side tubes uniformly in a known screen position without tilt or variation from one tube to another. To provide for this, a small centering magnet is placed on the outside of the tube envelope to project a mag netic field into the tube influencing the position of the electron beam. The magnet is held in' place by a thin web of mu metal or other low permeability magnetic material having an adhesive coating and surrounding the magnet to hold it in place on the tube envelope and to confine the magnetic field of the magnet which would otherwise project away from the tube envelope and disturb the beam in an adjacent tube. Thus, inexpensive cylindrical tubes can be placed closely adjacent each other to produce a line of text of any desired character shape which is carefully aligned from character to character in a single viewing plane. The foregoing and further features objectives and'advantages of the invention will be found in a preferred embodiment of the invention illustrated in the accompanying drawing, wherein:

FIG. 1 is a block schematic diagram of a display system,

FIG. 2 is a perspective view, partly broken away, of a CRT character display tube afforded by this invention, and

FIG. 3 is a plan view of beam alignment means provided in accordance with this invention.

As may be seen from FIG. 1, a row of visual display tubes 10, 10' etc. may be aligned in a row side-by-side along axis 12 to produce a line of characters individually produced in separate ones of the tubes 10. The tubes 10 arecathode-ray tubes electrostatically deflected by conventional internal plates by means of a character generator and selection circuit 15, which individually operates each tube 10, 10 etc. by means of a corresponding section 16, I6 etc. Thus leads l8 and 19 are electrically connected to produce two dimensions of scanning of the electron beam across the phosphorescent screens of the tubes, which are usually aligned in a single plane. Grid lead 17 can be used for selection of the tubes by means of conventional electronic modulation methods. Character generation methods of various sorts for deflecting cathode-ray beams to form visible characters are well known in the art as illustrated for example by U.S. Pat. No. 3,432,845 issued Mar. 1 l, l969, and such may be used in the block circuit 15 illustrated in FIG. 1 of this Specification.

For reference of different character positions the vertical axis 11 is shown for each tube 10 as well as the aligned horizontal axis 12. If the dots representing static beam position in tubes 10 and 10 are considered, it is evident that they may fall at nonuniform positions. If the reference position desired is in the center of the tube at the crossing point of the two axes, then the beams of tubes 10 and 10 would be misaligned. Any misalignment of the position of the characters or their inclination is readily detected by viewing and the orientation of the characters 2 in tubes 10" and 10 represent the situation encountered if the beam position of each tube is not carefully controlled.

In practice, if each tube is made so carefully that exact beam alignment is maintained from tube to tube, the cost becomes of the critical nature of the electrode positioning within a cathode-ray tube and the difficulty in aligning an electron gun axis identically in every tube. Also if the conventional methods of providing alignment potential adjusting means such as used for usual oscillographically produced displays, such as providing an adjustable resistor for both the vertical and horizontal axis, the cost of a display system using several tubes becomes excessive.

Also the use of standard beam centering methods such as the use of a magnet about the gun portion of the tube to influence the beam, illustrated for example by U.S. Pat. No. 3,302,049 issued Jan. 31, 1967, is not feasible because of the necessity of placing the cylindrical display tubes 10 as seen from FIG. 2 side-by-side so closely together that any centering magnet method of the prior art used to correct beam position Therefore it has been necessary to provide different and nonconventional beam alignment means effective at low cost to resolve the shortcomings of prior art devices. in accordance with this invention therefore, the means illustrated in FIGS. 2 and 3 includes a thin flat permanent magnet 33, placed adjacent the tube envelope 36 to project a field 34 into the electron gun 30 used to affect the beam position with respect to the tube axis 32 by choosing the proper position outside the tube envelope while viewing a beam reference position on the tube face. The magnet is then held against the tube envelope in its place by a thin web or strip of mu metal 35 or the like, which has a layer 37 of adhesive which adheres the assembly to the tube at a magnetically permeable position outside electron gun 30.

The tube is constructed with the electron gun parts held in glass beads 31 to nominally orient the beam and direct it along center line 32. However, very slight variations of tolerances in critical electrode and gun positions require the need for the alignment magnet 33. For example, the positioning of the button 29 from which the standard pins 28 and evacuation stem 39, extend may not be exactly aligned with the cylinder of tube envelope 10, in manufacture, or deflecting electrodes might have slight defects.

Not only does the adhesive coated web 35 provide for a convenient and inexpensive mount for magnet 33 which does not take up space preventing the cylindrical tubes to be placed side-by-side, but its low magnetic reluctance provides a preferred path for the magnetic field from magnet 33 which otherwise would leave the vicinity of the tube envelope and disturb the beam operation in an adjacent tube.

Thus, magnetic field lines 38 are confined by a high permeability mu metal shield 35 so that the tubes may be standardized for character alignment simply and effectively.

What I claim is:

l. A character display system having a plurality of side-byside cathode-ray tubes each displaying separate characters comprising in combination each said tube having an envelope of substantially cylindri cal form with a closed transparent end member including a phosphorescent coating upon which the cathode-ray impinges and electrostatic deflection means, to deflect the cathode-ray beam in two dimensions to produce a pattern upon said phosphorescent coating representative of characters such as alphanumeric displays,

means forming separate characters upon separate tubes aligned is said side-by-side array to provide an intelligible message thereupon by producing deflection potentials at said electrostatic deflection means, and

means for aligning the beams in all said side-by-side tubes to present uniform positioning of each of the characters when said cylindrical envelopes are placed closely together with each phosphor coating substantially aligned in a single plane and each electron gun portion of the respective cathode-ray tubes disposed at a standard distance from said single plane,

said means for aligning the beams being a thin permanent magnet structure placed alongside the outer envelope of each tube alongside the electron gun to project a magnetic field into said tube to influence the position of the electron beam formed by said gun wherein said magnet structure is covered by a thin web of high permeability magnetic material surrounding the magnet to confine the magnetic field of said magnet which otherwise would project away from the tube envelope to a region defined by said low permeability magnetic material near the tube envelope,

whereby, each of said tubes may have a magnetic centering device when placed closely adjacent a further tube that does not substantially influence the electron beam of the adjacent tube.

2. A system as defined in claim 1 wherein the thin web of low permeability magnetic material has an adhesive coating which adheres it to the outer envelope surface of the tube surrounding the electron un. I

3. A cathode-ray tu e electron beam posrtiontng device affixed onto the outer envelope surface of a cathode-ray tube having a magnetically permeable envelope surrounding the electron gun thereof comprising a magnet oriented to project a magnetic field through said envelope into said gun to influence the position of said beam and a thin web of low permeability magnetic material surrounding the magnet and holding it against the envelope to thereby confine the magnetic field of said magnet which otherwise would project away from the tube envelope to a region defined by said low permeability magnetic material near the tube envelope.

4. A device as defined in claim 3 wherein said web of low permeability magnetic material has an adhesive coating which adheres to the outer envelope surface of the tube surrounding said gun. 

1. A character display system having a plurality of side-by-side cathode-ray tubes each displaying separate characters comprising in combination each said tube having an envelope of substantially cylindrical form with a closed transparent end member including a phosphorescent coating upon which the cathode-ray impinges and electrostatic deflection means, to deflect the cathode-ray beam in two dimensions to produce a pattern upon said phosphorescent coating representative of characters such as alphanumeric displays, means forming separate characters upon separate tubes aligned is said side-by-side array to provide an iNtelligible message thereupon by producing deflection potentials at said electrostatic deflection means, and means for aligning the beams in all said side-by-side tubes to present uniform positioning of each of the characters when said cylindrical envelopes are placed closely together with each phosphor coating substantially aligned in a single plane and each electron gun portion of the respective cathode-ray tubes disposed at a standard distance from said single plane, said means for aligning the beams being a thin permanent magnet structure placed alongside the outer envelope of each tube alongside the electron gun to project a magnetic field into said tube to influence the position of the electron beam formed by said gun wherein said magnet structure is covered by a thin web of high permeability magnetic material surrounding the magnet to confine the magnetic field of said magnet which otherwise would project away from the tube envelope to a region defined by said low permeability magnetic material near the tube envelope, Whereby, each of said tubes may have a magnetic centering device when placed closely adjacent a further tube that does not substantially influence the electron beam of the adjacent tube.
 2. A system as defined in claim 1 wherein the thin web of low permeability magnetic material has an adhesive coating which adheres it to the outer envelope surface of the tube surrounding the electron gun.
 2. A system as defined in claim 1 wherein the thin web of low permeability magnetic material has an adhesive coating which adheres it to the outer envelope surface of the tube surrounding the electron gun.
 3. A cathode-ray tube electron beam positioning device affixed onto the outer envelope surface of a cathode-ray tube having a magnetically permeable envelope surrounding the electron gun thereof comprising a magnet oriented to project a magnetic field through said envelope into said gun to influence the position of said beam and a thin web of low permeability magnetic material surrounding the magnet and holding it against the envelope to thereby confine the magnetic field of said magnet which otherwise would project away from the tube envelope to a region defined by said low permeability magnetic material near the tube envelope.
 4. A device as defined in claim 3 wherein said web of low permeability magnetic material has an adhesive coating which adheres to the outer envelope surface of the tube surrounding said gun. 